// SPDX-License-Identifier: GPL-2.0+
/*
 *  flexible mmap layout support
 *
 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
 * All Rights Reserved.
 *
 * Started by Ingo Molnar <mingo@elte.hu>
 */

#include <linux/elf-randomize.h>
#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/random.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <asm/elf.h>

static unsigned long stack_maxrandom_size(void)
{
        if (!(current->flags & PF_RANDOMIZE))
                return 0;
        return STACK_RND_MASK << PAGE_SHIFT;
}

static inline int mmap_is_legacy(const struct rlimit *rlim_stack)
{
        if (current->personality & ADDR_COMPAT_LAYOUT)
                return 1;
        if (rlim_stack->rlim_cur == RLIM_INFINITY)
                return 1;
        return sysctl_legacy_va_layout;
}

unsigned long arch_mmap_rnd(void)
{
        return (get_random_u32() & MMAP_RND_MASK) << PAGE_SHIFT;
}

static unsigned long mmap_base_legacy(unsigned long rnd)
{
        return TASK_UNMAPPED_BASE + rnd;
}

static inline unsigned long mmap_base(unsigned long rnd,
                                      const struct rlimit *rlim_stack)
{
        unsigned long gap = rlim_stack->rlim_cur;
        unsigned long pad = stack_maxrandom_size() + stack_guard_gap;

        /* Values close to RLIM_INFINITY can overflow. */
        if (gap + pad > gap)
                gap += pad;

        /*
         * Top of mmap area (just below the process stack).
         * Leave at least a ~128 MB hole.
         */
        gap = clamp(gap, SZ_128M, (STACK_TOP / 6) * 5);

        return PAGE_ALIGN(STACK_TOP - gap - rnd);
}

static int get_align_mask(struct file *filp, unsigned long flags)
{
        if (filp && is_file_hugepages(filp))
                return huge_page_mask_align(filp);
        if (!(current->flags & PF_RANDOMIZE))
                return 0;
        if (filp || (flags & MAP_SHARED))
                return MMAP_ALIGN_MASK << PAGE_SHIFT;
        return 0;
}

unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
                                     unsigned long len, unsigned long pgoff,
                                     unsigned long flags, vm_flags_t vm_flags)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        struct vm_unmapped_area_info info = {};

        if (len > TASK_SIZE - mmap_min_addr)
                return -ENOMEM;

        if (flags & MAP_FIXED)
                goto check_asce_limit;

        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
                    (!vma || addr + len <= vm_start_gap(vma)))
                        goto check_asce_limit;
        }

        info.length = len;
        info.low_limit = mm->mmap_base;
        info.high_limit = TASK_SIZE;
        info.align_mask = get_align_mask(filp, flags);
        if (!(filp && is_file_hugepages(filp)))
                info.align_offset = pgoff << PAGE_SHIFT;
        addr = vm_unmapped_area(&info);
        if (offset_in_page(addr))
                return addr;

check_asce_limit:
        return check_asce_limit(mm, addr, len);
}

unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
                                             unsigned long len, unsigned long pgoff,
                                             unsigned long flags, vm_flags_t vm_flags)
{
        struct vm_area_struct *vma;
        struct mm_struct *mm = current->mm;
        struct vm_unmapped_area_info info = {};

        /* requested length too big for entire address space */
        if (len > TASK_SIZE - mmap_min_addr)
                return -ENOMEM;

        if (flags & MAP_FIXED)
                goto check_asce_limit;

        /* requesting a specific address */
        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
                                (!vma || addr + len <= vm_start_gap(vma)))
                        goto check_asce_limit;
        }

        info.flags = VM_UNMAPPED_AREA_TOPDOWN;
        info.length = len;
        info.low_limit = PAGE_SIZE;
        info.high_limit = mm->mmap_base;
        info.align_mask = get_align_mask(filp, flags);
        if (!(filp && is_file_hugepages(filp)))
                info.align_offset = pgoff << PAGE_SHIFT;
        addr = vm_unmapped_area(&info);

        /*
         * A failed mmap() very likely causes application failure,
         * so fall back to the bottom-up function here. This scenario
         * can happen with large stack limits and large mmap()
         * allocations.
         */
        if (offset_in_page(addr)) {
                VM_BUG_ON(addr != -ENOMEM);
                info.flags = 0;
                info.low_limit = TASK_UNMAPPED_BASE;
                info.high_limit = TASK_SIZE;
                addr = vm_unmapped_area(&info);
                if (offset_in_page(addr))
                        return addr;
        }

check_asce_limit:
        return check_asce_limit(mm, addr, len);
}

/*
 * This function, called very early during the creation of a new
 * process VM image, sets up which VM layout function to use:
 */
void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
{
        unsigned long random_factor = 0UL;

        if (current->flags & PF_RANDOMIZE)
                random_factor = arch_mmap_rnd();

        /*
         * Fall back to the standard layout if the personality
         * bit is set, or if the expected stack growth is unlimited:
         */
        if (mmap_is_legacy(rlim_stack)) {
                mm->mmap_base = mmap_base_legacy(random_factor);
                mm_flags_clear(MMF_TOPDOWN, mm);
        } else {
                mm->mmap_base = mmap_base(random_factor, rlim_stack);
                mm_flags_set(MMF_TOPDOWN, mm);
        }
}

static pgprot_t protection_map[16] __ro_after_init;

void __init setup_protection_map(void)
{
        pgprot_t *pm = protection_map;

        pm[VM_NONE]                                     = PAGE_NONE;
        pm[VM_READ]                                     = PAGE_RO;
        pm[VM_WRITE]                                    = PAGE_RO;
        pm[VM_WRITE | VM_READ]                          = PAGE_RO;
        pm[VM_EXEC]                                     = PAGE_RX;
        pm[VM_EXEC | VM_READ]                           = PAGE_RX;
        pm[VM_EXEC | VM_WRITE]                          = PAGE_RX;
        pm[VM_EXEC | VM_WRITE | VM_READ]                = PAGE_RX;
        pm[VM_SHARED]                                   = PAGE_NONE;
        pm[VM_SHARED | VM_READ]                         = PAGE_RO;
        pm[VM_SHARED | VM_WRITE]                        = PAGE_RW;
        pm[VM_SHARED | VM_WRITE | VM_READ]              = PAGE_RW;
        pm[VM_SHARED | VM_EXEC]                         = PAGE_RX;
        pm[VM_SHARED | VM_EXEC | VM_READ]               = PAGE_RX;
        pm[VM_SHARED | VM_EXEC | VM_WRITE]              = PAGE_RWX;
        pm[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]    = PAGE_RWX;
}

DECLARE_VM_GET_PAGE_PROT